Determination of diclofop-methyl and diclofop residues in soil and crops by gas chromatography.

A method is described for the determination of residues of the herbicide diclofop-methyl and its metabolite, diclofop, in soil and crops. The residues were extracted with acetone-light petroleum and extracts were concentrated (diclofop was derivatized to its pentafluorobenzyl derivative), and then the products were purified on a chromatographic column containing alumina, silver-alumina and Florisil. Finally, they were determined by gas chromatography using an electron-capture detector. The detection limits of diclofop-methyl and diclofop were between 0.01 and 0.05 mg/kg. The average recoveries were 76.4-97.2% and 72.8-105.2%, respectively, making the method suitable for statutory residue testing purposes.

Multiresidue screening method for fresh fruits and vegetables with gas chromatographic/mass spectrometric detection.

A gas chromatographic/mass spectrometric (GC/MS) screening method has been developed for the determination of pesticide residues in a variety of crop samples. Samples are extracted with acetonitrile and partitioned with sodium chloride saturated aqueous solution. Targeted pesticide analytes are separated on a short, narrow bore capillary column, identified by electron ionization MS scanned from 100 to 400 amu, and quantitated by the monitoring of base ions and internal standards. The accuracy of the quantitative determination measured in terms of average percentage recovery of 143 compounds in 13 crop samples was 92% with a relative standard deviation of 22%.

[Non-volatile nitrosamines in some foods from Linxian County].

For the incidence of non-volatile nitrosamines in the staple foods and vegetables, corn, millet, turnip and turnip chips collected from Linxian County Henan Province, a high incidence area of esophageal cancer, were collected, analyzed and compared with the foods from Huairou County Beijing, a low risk area. Nitrososarcosine (NSAR), nitrosoproline (NPRO) and two unknown non-volatile compounds were found in the food samples from Linxian, and the levels of NSAR in corn ranged 0.7-1.1 ppb and in turnip chips ranged 20.5-962.5 ppb. NSAR level detected in corn samples from Huairou County was not significantly different from that of Linxian. The possibility that the high content of nitrosamines in turnip chips is due to microbial infections is discussed.

Malate content of picoliter samples of Raphanus sativus cytoplasm.

Malate, which plays many essential roles in plant metabolism, is a potent in vitro inhibitor of the cytosolic enzyme phosphoenolpyruvate carboxylase (PEPC). Because PEPC activity leads to malate biosynthesis, malate is assumed to attenuate its own synthesis in situ. To test this hypothesis, we measured directly the malate content of picoliter samples of Raphanus root-hair cytoplasm using quantitative histochemical techniques. We also obtained an estimate for malate accumulation in these cells. These values were compared with the PEPC activity of individual root hairs (less than 2 ng). The results indicate that high cytoplasmic malate concentration does not severely inhibit PEPC in situ. We suggest that the focus for studies on the regulation of organic anion accumulation be on the interactive effects of malate and other PEPC effectors.

Selective determination of altertoxins by high-performance liquid chromatography with electrochemical detection with dual "in-series" electrodes.

A selective method for the determination of altertoxin-I and altertoxin-II by high-performance liquid chromatography with electrochemical detection is described. Altertoxins were separated on a reversed-phase column with methanol-water containing 0.1 M sodium nitrate and 1 mM nitric acid (60:40) as eluent and detected with dual in-series electrodes operating in the "redox" mode (generator electrode +1.0 V, indicator electrode -0.1 V). The method was applied successfully to the determination of sub-ppm levels of altertoxins in samples of maize, rice and tomatoes infected by Alternaria alternata.

Determination of nabam fungicide in crops by liquid chromatography with postcolumn reaction detection.

The ethylenebisdithiocarbamate (EBDC) fungicide, nabam, was determined in several crop matrixes using liquid chromatography with postcolumn reaction detection. After separation by micellar liquid chromatography, nabam (EBDC sodium salt) was acid hydrolyzed to ethylenediamine and fluorigenically labeled with o-phthalaldehyde-mercaptoethanol (OPA-MERC). Standard curves were linear from the detection limit of ca 1 ng to 1000 ng. Nabam was recovered in high yield (89 plus or minus 7.7%) over a range of concentrations (0.1 to 20 ppm) from fortified samples of papaya, lettuce, cucumber, spinach, and applesauce using a simple extraction method. Efforts to convert the more popular EBDC fungicides, maneb and mancozeb, to nabam are discussed.

[Hygienic evaluation of nitrate levels in drinking water and vegetable food products in various regions of Lithuania]. / Gigienicheskaia otsenka soderzhaniia nitratov v pit'evoi vode i rastitel'nykh pishchevykh produktakh nekotorykh raionov Litovskoi SSR.

Significantly higher nitrate content was detected in drinking water and vegetables grown by the rural population in the regions where industrial enterprises producing chemical fertilizers are located, as compared to the control regions. It has been concluded that a special attention should be paid to the daily level of nitrates ingested by the population (especially by children) in the industrial regions of the Republic and to their health state.

Estimating human exposure through multiple pathways from air, water, and soil.

This paper describes a set of multipathway, multimedia models for estimating potential human exposure to environmental contaminants. The models link concentrations of an environmental contaminant in air, water, and soil to human exposure through inhalation, ingestion, and dermal-contact routes. The relationship between concentration of a contaminant in an environmental medium and human exposure is determined with pathway exposure factors (PEFs). A PEF is an algebraic expression that incorporates information on human physiology and lifestyle together with models of environmental partitioning and translates a concentration (i.e., mg/m3 in air, mg/liter in water, or mg/kg in soil) into a lifetime-equivalent chronic daily intake (CDI) in mg/kg-day. Human, animal, and environmental data used in calculating PEFs are presented and discussed. Generalized PEFs are derived for air----inhalation, air----ingestion, water----inhalation, water----ingestion, water----dermal uptake, soil----inhalation, soil----ingestion, and soil----dermal uptake pathways. To illustrate the application of the PEF expressions, we apply them to soil-based contamination of multiple environmental media by arsenic, tetrachloroethylene (PCE), and trinitrotoluene (TNT).

The assessment of radiocaesium intake from food using duplicate diet and whole-body monitoring techniques.

A duplicate diet study has been carried out on a group of Harwell employees in order to investigate the food types in which radiocaesium from Chernobyl was most likely to be found, and also the intake of radiocaesium in food with relation to observed whole-body levels. The duplicate diet study indicated that the highest levels of radiocaesium were in milk and meat or fruit and vegetables. Radiocaesium concentrations in food of all types are small compared to the most restrictive generalized derived limit. Daily intakes of radiocaesium measured by the diet study, of the order of 2-3 Bq day-1, generally agreed with values calculated from whole-body measurements. Committed does from radiocaesium have been estimated from dietary intakes to be in the range 3-29 muSv year-1, while whole-body measurements indicate a range of 6-18 muSv year-1; these doses are small compared to other sources of internal irradiation and to recommended limits.

Fruits and vegetables are a source of galactose: implications in planning the diets of patients with galactosaemia.

It has become apparent that removing dairy products from the diets of patients with galactosaemia does not sufficiently diminish the deleterious signs. We have determined the amount of soluble monomeric galactose in 45 fruits and vegetables using capillary gas chromatography and selective ion monitoring. Galactose contents ranged from less than 0.1 mg per 100 g of tissue in artichoke, mushroom, olive, and peanut to 35.4 mg per 100 g in persimmon. Fruits and vegetables with over 10 mg per 100 g included date, papaya, bell pepper, tomato and watermelon. These results will provide important data for planning the diets of patients with galactosaemia.

Thermal degradation of carotenes and influence on their physiological functions.

Raw carrot juice contains a considerable amount of alpha- and beta-carotene, which makes carrot an excellent source of vitamin A. Heat treatment of the juice at temperatures comparable to those at pasteurization and boiling does not change the carotenes, while heating at temperatures used during sterilization results in rearrangement of the carotene molecules and a decrease in total carotenes. The all-trans alpha- and beta-carotenes appear partly as cis-isomers, especially the 13-cis-isomer. Isomerization of the carotenes leads to a decrease in their vitamin A activity. Carotenes also seem to be anticarcinogens but the extent to which this property is influenced by isomerization is still unknown.

Chemical composition of kernels from some species of Cucurbitaceae grown in Nigeria.

The seeds of lesser-known species - Cucumeropsis mannii, Lagenaria sicceraria varieties 1 and 2 and Telfairia occidentalis, of Cucurbitaceae family were studied. The protein content of C. mannii was 36.1% and the varieties 1 and 2 of L. sicceraria had 32.1% and 33.3% respectively. Telfairia occidentalis had protein content of 33.2%. The fat contents of C. mannii, L. Sicceraria var. 1 and 2 and T. occidentalis were 44.4%, 44.6%, 46.9% and 42.3% respectively. The crude fibre content for each of the two varieties of L. sicceraria was 3.6% and T. occidentalis had 5.5%. Cucumeropsis mannii had the lowest (2.4%) fibre content. The carbohydrate contents for L. Sicceraria var. 2, C. mannii, and T. occidentalis were 12.6%, 13.2% and 14.4% respectively. Lagenaria sicceraria var. 1 had the highest value of carbohydrate (15.8%). The species were relatively rich in potassium and magnesium with range of values of 0.56% to 0.68% and 434 ppm to 444 ppm respectively. Cucumeropsis mannii and Lagenaria sicceraria var. 2 had relatively high contents of calcium (117 ppm) and iron (109 ppm) respectively. The kernels of these species exhibited lipase activity. Telfairia occidentalis showed the highest degree of lipase activity.

Structural and geometrical isomers of carotenoids in human plasma.

We have quantitatively analyzed human plasma for the following carotenoids: all-trans-lutein, all-trans-zeaxanthin, alpha-cryptoxanthin, beta-cryptoxanthin, the sum of all-trans-lycopene and its cis isomers, alpha-carotene and beta-carotene. In addition, we have tentatively identified and quantified 13-cis-lutein and 13-cis-zeaxanthin in human plasma. The latter two cis isomers are also apparent in samples of two common food items, spinach and corn meal. We have analyzed the ratios of all of the members of the beta, beta family of carotenoids (zeaxanthin, beta-cryptoxanthin and beta-carotene) to their corresponding beta, epsilon structural isomers (lutein, alpha-cryptoxanthin and alpha-carotene) in human plasma. There are marked differences in these ratios, with beta-carotene and beta-cryptoxanthin predominating in the carotene and monohydroxy-xanthophyll classes and lutein predominating in the dihydroxy-xanthophyll class. These differences could be attributable to dietary intake or to specific mechanisms in the way humans absorb and utilize these compounds.

Severe phototoxic burn following celery ingestion.

A 65-year-old woman developed a severe, generalized phototoxic reaction following a visit to a suntan parlor. History taking revealed that she had consumed a large quantity of celery root (Apium graveolens) 1 hour earlier. With the use of thin-layer chromatography, methoxsalen (8-methoxypsoralen) and 5-methoxypsoralen were identified in the extract from a similar celery root. The biologic activity of this extract, as evaluated with the semiquantitative Candida albicans inhibition technique, indicated a total psoralen dose of approximately 45 mg. Substantial amounts of psoralen may be absorbed from vegetables, such as celery, and under unusual circumstances, this may constitute a health hazard.

Determination of L-ascorbic acid in fruit and vegetable juices by flow injection with immobilised ascorbate oxidase.

Ascorbate oxidase was immobilised on cyanogen bromide activated-Sepharose 4B and incorporated in a flow-injection system with amperometric detection at a glassy carbon electrode at +0.6 V. On passage through the immobilised ascorbate oxidase a fraction of the L-ascorbic acid was converted into dehydroascorbic acid and the decrease in signal was measured. This could be directly related to the amount of L-ascorbic acid present. The calibration graph was linear over the range 0-400 ng ml(-1) with a correlation coefficient of 0.9994. The detection limit (2 sigma) in phosphate buffer (0.08 M, pH 5.5) was 4.0 ng ml(-1). The relative standard deviation for a 200 ng ml(-1) standard was 1.0% (n = 10) and the sampling throughput was 30 samples h(-1). The method was used for the simple and rapid determination of L-ascorbic acid in fruit and vegetable juice.

Purification and complete amino acid sequence of a new type of sweet protein taste-modifying activity, curculin.

A new taste-modifying protein named curculin was extracted with 0.5 M NaCl from the fruits of Curculigo latifolia and purified by ammonium sulfate fractionation, CM-Sepharose ion-exchange chromatography, and gel filtration. Purified curculin thus obtained gave a single band having a Mr of 12,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the presence of 8 M urea. The molecular weight determined by low-angle laser light scattering was 27,800. These results suggest that native curculin is a dimer of a 12,000-Da polypeptide. The complete amino acid sequence of curculin was determined by automatic Edman degradation. Curculin consists of 114 residues. Curculin itself elicits a sweet taste. After curculin, water elicits a sweet taste, and sour substances induce a stronger sense of sweetness. No protein with both sweet-tasting and taste-modifying activities has ever been found. There are five sets of tripeptides common to miraculin (a taste-modifying protein), six sets of tripeptides common to thaumatin (a sweet protein), and two sets of tripeptides common to monellin (a sweet protein). Anti-miraculin serum was not immunologically reactive with curculin. The mechanism of the taste-modifying action of curculin is discussed.

[Radiation-hygienic evaluation of vegetables and potatoes grown after soil irrigation with water containing artificial radionuclides]. / Radiatsionno-gigienicheskaia otsenka ovoshchnoi produktsii i kartofelia, vozdelyvaemykh pri oroshenii vodami, soderzhashchimi iskusstvennye radionuklidy.

Radiation and hygienic appraisal of vegetables cultivated under various kinds of irrigation is presented. Critical radionuclides are determined along with major vegetable products owing to which the great amount of radionuclides is absorbed. Contribution of vegetables and potato cultivated under irrigation into the total body intake of radionuclides by local residents has been evaluated.